US1380498A - Phonographic reproducer - Google Patents

Description

L. C. PETTITT.

PHONOGRAPIC REPRODUCER.

APPLICATION FILED JULY 10, I919.

Patented June 7, 1921.

UNITED STATES PATENT OFFICE.

PHONOGRAIPHIG REPRODUCER.

Specification of Letters Patent.

Patented June a, 1921.

Application filed July 10, 1919. Serial No. 309,892.

'ing,I forming a part of this speci cation.

y invention relates to phonographic reproducers, and particularly to the diaphragm 4 and associated parts thereof.

The general object of the present invention resides in the provision of a phonographic I reproducer having louder and clearer tone or sound-reproducing qualities, and which is practically non-breakable or damageable.

This and other objects. of the present invention will be pointed out in detail in connection with the accompanying drawing showing one form of reproducer constructed in. accordance with my invention. Although I have illustrated a reproducer adapted for use only on the lateral groove form of record, I wish it to be understood that my invention may be applied to'the hill and dale groove record, in which case the diaphragm of the reproducer lies parallel to the face of the record.

Referring to the accompanying drawing,

ldesignates a reproducer or sound-box casing attached to a tube 2 extending to the resonator or horn of the instrument. The reproducer casing 1 supports the diaphragm 3 which is connected at its geometrical center with the upper end of a stylus lever 4 pivoted to the casing as shown at 5. The lower or free end of the stylus lever 4 is provided with the usual stylus or needle socket 6 and stylus screw 7 for clamping the stylus 8 onto the lever. of aluminum alloyed with magnesium or some other metal which will increase the stiffness and resiliency of the aluminum. In the preferred form of my invention, I form this diaphragm of lumlnum alloyed with not to exceed five per cent. magnesium. This five per cent. is not a critical or limiting amount. I have found, however, that excellent results are secured in the use of an alloy in which the magnesium content is slightly less than five per cent. Such an alloy is quite springy, it has a close hard grain, its specific gravity is low, it does not readily The diaphragm 3 is formed tarnish or corrode, it does not split or cleave as does mica, it is relatively inexpensive and it is capable of withstanding comparatively rough handling.

. I propose further to construct the lever 4 and stylus 8 of the same material as that of the dlaphragm, with the result that the v brations produced by the record are carrled through the instrument by the same or homogeneous metal, and the tone or sound reproduced is clear and distinct.

I am not certain that I can give a correct, sclentific explanation of the reasons for the excellent results secured in the use of a phonographic reproducer equipped with a diaphragm of an aluminum alloy as previously described. I do know from repeated experiment and test that when such aluminum alloy diaphragm is used, the tone qual- 1ty is very much improved over that which I have been able to secure in the use of mica.

There is greater fidelity in the reproduction of the human voice and in the reproduction of the tones of certain musical instruments, particularly, for example, the treble part of the scale of a piano. I attribute this in creased fidelity of. reproduction to a more complete and perfect reproduction of the vibrations of the sound waves. I believe that the extreme lightness of this aluminum alloy makes it very free to respond tothevibrations impressed upon it by the stylus. I believe that its very considerable 'stiflness and springiness causes the diaphragm to fol low rapidly and exactly the slower and more rapid vibrations of the stylus, which correspond with the over-tones of thesound to be reproduced. This alloy has what may be described, perhaps, as a natural bell-like quality. Its superiority in this respect may be due to the hardness, closeness-and more erfect homogeneity of the metal. While am not certain therefore, I believe that the superiority of this aluminum alloy for the diaphragms of phonographic reproducers is due to its lightness, its stiffness, its springiness and its hard, close homogeneous grain. I do know that the results secured from the use of these diaphragms are excellent.

Although I have described my invention as applied to phonographic reproducers, it will be apparent that certain of the improved arrangements can be applied to phonographic recorders without departing from the spirit and scope of the present invention.

Having thus described my invention, What 'I claim is 1. A phonograph reproducer diaphragm formed of a malleable, fine grained, springy' 5 alloy of aluminum.

. 2. A phonograph reprodueerdiaphragm formed of a malleable, springy, and fine grained magnesium alloy of aluminum.

3. A phonograph reproducer diaphragm 10 formed of a hard, malleable, springy, and

fine grained magnesium alloy of aluminum in which the percentage of magnesium does not exceed five per cent. y

In Witness whereoflI hereunto subscribe my name this 7th day of July, 1919.

' C. PETTITT.

Witnesses: i

MARY A. 0001:, ANDREW WINTERCORN.

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